Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Physics B Atomic Molecular and Optical Physics

Electronic ring current and magnetic field generation induced by current-carrying states of ring molecules in intense fields

Qing-Yun Xu, Yong-Lin He, Shu-Juan Yan, Jing Guo

Published Dec 15, 2022• 4 citations
Publisher

Abstract

Abstract The generation of electronic currents and magnetic fields by H 6 5 + and H 4 3 + molecules with current-carrying states under circularly polarized (CP) and linearly polarized (LP) laser pulses is investigated. Results show that the electronic currents and magnetic fields induced by CP pulses are higher than those by LP pulses for both molecules in the resonance excitation scheme. This can be attributed to the switchable dipole moment of the laser pulses, inducing selective state-to-state electronic transitions. Moreover, it was found that magnetic fields are sensitive to different initial states of the molecules in the ionization scheme. In particular, the magnetic fields induced by the current-carrying states are much higher than that induced by the ground state, which is because the current-carrying states have a stable electronic ring current and the induced magnetic field is contributed by the current-carrying state itself and the laser field. These findings provide a scheme for generating ring-shaped currents and magnetic fields in molecular systems for future research in ultrafast magneto-optics.

DOI
10.1088/1361-6455/acabf1

Related papers

Generation of Ultrafast Attosecond Magnetic Field from Ne Dimer in Circularly Polarized Laser Pulses

Shujuan 淑娟 Yan 闫, Qingyun 清芸 Xu 徐, Xinyu 欣宇 Hao 郝 +2 more

By numerically solving time-dependent Schrödinger equations, we investigate the generation of electron currents, ultrafast magnetic fields and photoelectron momentum distributions (PMD) when circularly polarized laser pulses interact with a Ne dimer in the charge migration (CM) process. By adjusting the laser wavelength, we consider two cases: (i) coherent resonance excitation (λ = 76 nm) and (ii) direct ionization (λ = 38 nm). The results show that the current and magnetic field generated by the Ne dimer under resonance excitation are stronger than under direct ionization. This phenomenon is due to the quantum interference between the initial state 2pσ g and the excited state 3sσ g under resonance excitation, so the CM efficiency of the dimer can be improved and the strength of the PMD under different ionization conditions is opposite to the strength of the electron current and induced magnetic field. In addition, we also find that both 2pπ g and 2pπ u have coherent resonance excitation with 3sσ g state and generate periodic oscillating currents for the Ne dimer. The study of the dynamics of the Ne dimer under different ionization conditions lays a foundation for research of ultrafast magnetism in complex molecular systems.

Chinese Physics Letters•Sep 28, 2023•1 citation

Opportunities for detecting ring currents using an attoclock setup

Jivesh Kaushal, Felipe Morales, Olga V. Smirnova

Strong field ionization by circularly polarized laser fields from initial states with internal orbital momentum has an interesting propensity rule: electrons counter-rotating with respect to the laser field can be liberated more easily than co-rotating electrons [Barth and Smirnova, Phys. Rev. A 84, 063415 (2011)]. Here we show that application of few-cycle IR pulses allows one to use this propensity rule to detect ring currents associated with such quantum states, by observing angular shifts of the ejected electrons. Such shifts present the main observable of the attoclock method. We use time-dependent analytical $R$-matrix theory to show that the attoclock measured angular shifts of an electron originating from two counter-rotating orbitals (${p}^{+}$ and ${p}^{\ensuremath{-}}$) are noticeably different. Our work opens opportunities for detecting ring currents excited in atoms and molecules, using the attoclock setup.

arXiv:1510.01092•Physical Review A•Dec 7, 2015•41 citations

On the effects of absolute laser phase on the interaction of a pulsed laser with polar versus nonpolar molecules

Alex Brown, William J. Meath

The absolute laser phase dependence of the time-dependent populations of the molecular states, including the steady-state (long time) populations of the states, associated with the interaction of a molecule with a pulsed laser is investigated using illustrative two-level examples. One-photon transitions, including the effects of permanent dipoles, are discussed as a function of the pulse duration, intensity, and (absolute) laser phase, for selected laser frequencies. The effects of laser phase can be large, depending on the values of the pulse duration for a given frequency and intensity. The effects of permanent dipoles, relative to no permanent dipoles, are significant for large laser field strengths ε0. When the laser-molecule coupling parameter b=μ12ε0/E21⩾0.2, where μ12 and E21 are the transition dipole and energy difference between the ground and excited states, respectively, the dynamics of the pulse-molecule interaction are (strongly) phase dependent, independent of pulse duration, whereas the corresponding steady-state populations of the molecular states may or may not be phase-dependent depending on the pulse duration. Analytical rotating wave approximations for pulsed laser-molecule interactions are useful for interpreting the dynamics and the steady-state results as a function of field strength and pulse duration, including the effects of permanent dipole moments. The results reported in this paper are based on molecular parameters associated with an S0→S1 electronic transition in a dipolar molecule. However, they are presented in reduced form and therefore can be scaled to other regions of the electromagnetic spectrum. Short, intense pulses at or beyond the limits of current laser technology will often be required for the types of absolute laser phase effects of this paper to be appreciable for electronic excitations. The discussion, in the UV-VIS, also suffers from the use of a two-level model and from the requirement of field intensities that can be beyond the Keldysh limit. For other spectral regions, these absolute laser phase effects will be much more readily applicable.

The Journal of Chemical Physics•Dec 1, 1998•37 citations

Resonant third-harmonic generation in I2 with circularly polarized light

Chen-Yu Tai

Magnetic-field-induced resonant third-harmonic generation in ${\mathrm{I}}_{2}$ with circularly polarized light is studied. With a magnetic field perpendicular to the propagating direction of the light, the axial symmetry is broken and the angular momentum is no longer conserved in such a system, and the third harmonic may be generated under such conditions. Quantum beats in photon-echo-like third-harmonic generation with nonsynchronous laser pulses are also studied. The intensity of the harmonic generated may be interpreted in terms of the interference between a molecule and itself as well as the interference between different molecules. The gyromagnetic ratio of the resonant states is measured.

Physical Review A•Dec 1, 1983•6 citations

Nonadiabatic tunnel ionization of current-carrying orbitals of prealigned linear molecules in strong circularly polarized laser fields

Kunlong Liu, Ingo Barth

We derive the analytical formula of the ratio of the ionization rates of degenerate valence ${\ensuremath{\pi}}_{\ifmmode\pm\else\textpm\fi{}}$ orbitals of prealigned linear molecules in strong circularly polarized (CP) laser fields. Interestingly, our theory shows that the ionization ratio for molecular orbitals with opposite azimuthal quantum numbers $\ifmmode\pm\else\textpm\fi{}|m|$ (e.g., ${\ensuremath{\pi}}_{\ifmmode\pm\else\textpm\fi{}}$) is identical to that for atomic orbitals with the same $\ifmmode\pm\else\textpm\fi{}|m|$ (e.g., ${p}_{\ifmmode\pm\else\textpm\fi{}}$). In general, the electron counter-rotating to the CP laser field tunnels more easily, not only for atoms but also for linear molecules. Our theoretical predictions are then verified by numerically solving the three-dimensional time-dependent Schr\"odinger equation for the ionization of the prealigned nitric oxide (NO) molecule in strong CP laser fields. Due to the spin-orbital coupling in the electronic ground state of NO and the sensitivity of ionization to the sense of electron rotation, the ionization of NO in CP fields can produce spin-polarized photoelectrons with high controllability of spin polarization up to $100%$.

Physical Review A•Oct 3, 2016•30 citations

Electronic quantum coherence induced by strong field molecular ionization

Jinming Chen, Jinping Yao, Haisu Zhang +9 more

The existence of electronic coherence can fundamentally change the scenario of nonlinear interaction of light with quantum systems such as atoms and molecules, which, however, has escaped from observation in the investigations of strong field nonlinear optics in the past several decades. Here, we report on the generation of electronic quantum coherence by strong field ionization of nitrogen molecules in an intense 800 nm laser field. The coherence is experimentally revealed by observing a resonant four-wave mixing process in which the two pump pulses centered at 800 nm and 1580 nm wavelengths are temporally separated from each other. The experimental observation is further reproduced by calculating the nonlinear polarization response of N_2^+ ions using a three-level quantum model. Our result suggests that strong field ionization provides a unique approach to generating a fully coherent molecular wavepacket encapsulating the rotational, vibrational, and electronic states.

arXiv:1808.03914•Aug 12, 2018•0 citations
Abstract The generation of electronic currents and magnetic fields by H 6 5 + and H 4 3 + molecules with current-carrying states under circularly polarized (CP) and linearly polarized (LP) laser pulses is investigated. Results show that the electronic currents and magnetic fields induced by CP pulses are higher than those by LP pulses for both molecules in the resonance excitation scheme. This can be attributed to the switchable dipole moment of the laser pulses, inducing selective state-to-state electronic transitions. Moreover, it was found that magnetic fields are sensitive to different initial states of the molecules in the ionization scheme. In particular, the magnetic fields induced by the current-carrying states are much higher than that induced by the ground state, which is because the current-carrying states have a stable electronic ring current and the induced magnetic field is contributed by the current-carrying state itself and the laser field. These findings provide a scheme for generating ring-shaped currents and magnetic fields in molecular systems for future research in ultrafast magneto-optics.
By numerically solving time-dependent Schrödinger equations, we investigate the generation of electron currents, ultrafast magnetic fields and photoelectron momentum distributions (PMD) when circularly polarized laser pulses interact with a Ne dimer in the charge migration (CM) process. By adjusting the laser wavelength, we consider two cases: (i) coherent resonance excitation (λ = 76 nm) and (ii) direct ionization (λ = 38 nm). The results show that the current and magnetic field generated by the Ne dimer under resonance excitation are stronger than under direct ionization. This phenomenon is due to the quantum interference between the initial state 2pσ g and the excited state 3sσ g under resonance excitation, so the CM efficiency of the dimer can be improved and the strength of the PMD under different ionization conditions is opposite to the strength of the electron current and induced magnetic field. In addition, we also find that both 2pπ g and 2pπ u have coherent resonance excitation with 3sσ g state and generate periodic oscillating currents for the Ne dimer. The study of the dynamics of the Ne dimer under different ionization conditions lays a foundation for research of ultrafast magnetism in complex molecular systems.
Strong field ionization by circularly polarized laser fields from initial states with internal orbital momentum has an interesting propensity rule: electrons counter-rotating with respect to the laser field can be liberated more easily than co-rotating electrons [Barth and Smirnova, Phys. Rev. A 84, 063415 (2011)]. Here we show that application of few-cycle IR pulses allows one to use this propensity rule to detect ring currents associated with such quantum states, by observing angular shifts of the ejected electrons. Such shifts present the main observable of the attoclock method. We use time-dependent analytical RRR-matrix theory to show that the attoclock measured angular shifts of an electron originating from two counter-rotating orbitals (p+{p}^{+}p+ and ${p}^{\ensuremath{-}}$) are noticeably different. Our work opens opportunities for detecting ring currents excited in atoms and molecules, using the attoclock setup.
The absolute laser phase dependence of the time-dependent populations of the molecular states, including the steady-state (long time) populations of the states, associated with the interaction of a molecule with a pulsed laser is investigated using illustrative two-level examples. One-photon transitions, including the effects of permanent dipoles, are discussed as a function of the pulse duration, intensity, and (absolute) laser phase, for selected laser frequencies. The effects of laser phase can be large, depending on the values of the pulse duration for a given frequency and intensity. The effects of permanent dipoles, relative to no permanent dipoles, are significant for large laser field strengths ε0. When the laser-molecule coupling parameter b=μ12ε0/E21⩾0.2, where μ12 and E21 are the transition dipole and energy difference between the ground and excited states, respectively, the dynamics of the pulse-molecule interaction are (strongly) phase dependent, independent of pulse duration, whereas the corresponding steady-state populations of the molecular states may or may not be phase-dependent depending on the pulse duration. Analytical rotating wave approximations for pulsed laser-molecule interactions are useful for interpreting the dynamics and the steady-state results as a function of field strength and pulse duration, including the effects of permanent dipole moments. The results reported in this paper are based on molecular parameters associated with an S0→S1 electronic transition in a dipolar molecule. However, they are presented in reduced form and therefore can be scaled to other regions of the electromagnetic spectrum. Short, intense pulses at or beyond the limits of current laser technology will often be required for the types of absolute laser phase effects of this paper to be appreciable for electronic excitations. The discussion, in the UV-VIS, also suffers from the use of a two-level model and from the requirement of field intensities that can be beyond the Keldysh limit. For other spectral regions, these absolute laser phase effects will be much more readily applicable.
Magnetic-field-induced resonant third-harmonic generation in I2{\mathrm{I}}_{2}I2​ with circularly polarized light is studied. With a magnetic field perpendicular to the propagating direction of the light, the axial symmetry is broken and the angular momentum is no longer conserved in such a system, and the third harmonic may be generated under such conditions. Quantum beats in photon-echo-like third-harmonic generation with nonsynchronous laser pulses are also studied. The intensity of the harmonic generated may be interpreted in terms of the interference between a molecule and itself as well as the interference between different molecules. The gyromagnetic ratio of the resonant states is measured.
We derive the analytical formula of the ratio of the ionization rates of degenerate valence ${\ensuremath{\pi}}_{\ifmmode\pm\else\textpm\fi{}}$ orbitals of prealigned linear molecules in strong circularly polarized (CP) laser fields. Interestingly, our theory shows that the ionization ratio for molecular orbitals with opposite azimuthal quantum numbers $\ifmmode\pm\else\textpm\fi{}|m|$ (e.g., ${\ensuremath{\pi}}_{\ifmmode\pm\else\textpm\fi{}}$) is identical to that for atomic orbitals with the same $\ifmmode\pm\else\textpm\fi{}|m|$ (e.g., ${p}_{\ifmmode\pm\else\textpm\fi{}}$). In general, the electron counter-rotating to the CP laser field tunnels more easily, not only for atoms but also for linear molecules. Our theoretical predictions are then verified by numerically solving the three-dimensional time-dependent Schr\"odinger equation for the ionization of the prealigned nitric oxide (NO) molecule in strong CP laser fields. Due to the spin-orbital coupling in the electronic ground state of NO and the sensitivity of ionization to the sense of electron rotation, the ionization of NO in CP fields can produce spin-polarized photoelectrons with high controllability of spin polarization up to 100100%100.
The existence of electronic coherence can fundamentally change the scenario of nonlinear interaction of light with quantum systems such as atoms and molecules, which, however, has escaped from observation in the investigations of strong field nonlinear optics in the past several decades. Here, we report on the generation of electronic quantum coherence by strong field ionization of nitrogen molecules in an intense 800 nm laser field. The coherence is experimentally revealed by observing a resonant four-wave mixing process in which the two pump pulses centered at 800 nm and 1580 nm wavelengths are temporally separated from each other. The experimental observation is further reproduced by calculating the nonlinear polarization response of N_2^+ ions using a three-level quantum model. Our result suggests that strong field ionization provides a unique approach to generating a fully coherent molecular wavepacket encapsulating the rotational, vibrational, and electronic states.